Polyethylenepolyamines are commonly made industrially by the reaction of ethylene dichloride (EDC, 1,2-dichloroethane), with ammonia at elevated temperature and pressure to form a mixture of amine hydrochlorides. The amine hydrochlorides are treated with aqueous caustic to neutralize the hydrochloride and NaCl is produced as a by-product. Excess ammonia is removed and the amines are separated by distillation under vacuum in order to avoid degradation. The composition of the amine mixture can be varied by recycling one of the product amines which results in an increase in the amount of the amine next higher in the series to the one recycled. The process described is energy intensive because of the separations involved.
Another process (U.S. Pat. No. 4,647,701) for producing ethyleneamines involves reductive amination of monoethanolamine, which is passed over a nickel catalyst in the presence of hydrogen at a temperature of 150.degree. C. to 225.degree. C. and a pressure of 35 to 400 atm. In addition to the ethylenediamine (EDA) and diethylenetriamine (DETA),piperazine and substituted piperazines are produced. Although this process overcomes some of the difficulties of the EDC-NH.sub.3 process, it is unable to produce the desired higher polyamines without the concurrent production of undesired substituted piperazines.
More recently acid dehydration catalysts have been employed to react an alkanolamine with ammonia or an amine to produce non-cyclic polyamines. In U.S. Pat. No. 4,036,881 a catalyst for making polyamines is disclosed which contains a phosphorous substance, e.g. boron phosphate. Other patents for the reaction include phosphorus supported on titania (U.S. Pat. No. 4,524,143), zirconia (U.S. Pat. No. 3,358,029) and zirconium silicate (U.S. Pat. No. 3,321,506). Group IIIB metal acid phosphates (U.S. Pat. No. 4,463,193) have also been employed for the purpose.
Various sulfates, nitrates and phosphates also have been disclosed as catalysts for making amines. In a related reaction, a fluorosulfonic acid catalyst has been disclosed as useful for reacting an alkylene oxide with ammonia or an amine to prepare an alkanolamine (U.S. Pat. No. 4,605,769)